There is a three-way or four-way valve used for piping of air conditioner and the like as prior art of the present invention (refer to the patent reference 1 given below). Inside the piping of the refrigeration cycle in the air conditioner an operational fluid such as CO.sub.2 or the like is used as a refrigerant. In the refrigerant cycle using CO.sub.2 as operating fluid, generally the service pressure range becomes more than ten times compared with those of conventional refrigerants. The fact that the service pressure is high causes various problems to a switching valve. FIG. 4 illustrates a refrigeration cycle of this air conditioner. Also FIG. 5 illustrates a heating cycle of the air conditioner. In addition, FIG. 6 shows a full cross-sectional view of a three-way valve used in the cycles of FIG. 4 and FIG. 5.
100 in FIG. 4 and FIG. 5 designates a valve apparatus being comprised of a first three-way valve 100A and a second three-way valve 100B. This valve apparatus 100 communicates with the piping from a compressor 110. One side of piping of the valve apparatus 100 communicates with an outdoor heat exchanger 103. Also the other side of piping of the valve apparatus 100 communicates with an indoor heat exchanger 105. In addition, there is disposed an expansion valve 104 in the piping 106 which communicates the outdoor heat exchanger 103 with the indoor heat exchanger 105.
Next, one of the three-way valve 100A used in the refrigeration and heating cycles will be described using FIG. 6. The three-way valve 100A is comprised of a valve main body 200 and a solenoid valve 250. The valve main body 200 is comprised of a first valve portion 201, a second valve portion 211, a third valve portion 221 and a fourth valve portion 231.
In the first valve portion 201, a first valve body 202 in a spherical form is fitted in a first valve body bore 203 in freely moveable manner. On the hind side of the first valve body 202 is formed a first operation cavity 206. There is disposed a first spring 205 within the first operation cavity 206. This first spring 205 resiliently urges the first valve body 202 downward in the figure. And the first valve body 202 lifts from or rests on a first valve seat 204 during the operation.
The second valve portion 211 is arranged in symmetry to the first valve portion 201. And a second valve body 212 is fitted in a second valve body bore 213 in freely moveable manner. The second valve body 212 is resiliently urged by a second spring 215 which is disposed within a second operation cavity 216. Then the second valve body 212 lifts from or rests on a second valve seat 214 during the operation.
Next, the third valve portion 221 is arranged in parallel to the second valve portion 211. A third valve body 222 is fitted in a third valve body bore 223 in freely moveable manner. On the hind side of the third valve body 222 is formed a third operation cavity 226. The third valve body 222 is resiliently urged by a third spring 225 which is disposed within the third operation cavity 226. Then the third valve body 222 lifts from or rests on a third valve seat 224 during the operation.
In the fourth valve portion 231, a fourth valve body 232 is disposed at the frontal tip of a moveable attraction element 251. On the hind side of the moveable attraction element 251 is formed a fourth operation cavity, and a fourth spring 255 which is disposed within the fourth operation cavity resiliently urges the moveable attraction element 251. Surrounding of this fourth valve body 232 defines a fourth valve body bore 233. And the fourth valve body 232 lifts from or rests on a fourth valve seat 234. The fourth valve body 232 operates with the moveable attraction element 251 in an integral manner. This moveable attraction element 251 is attracted toward the fixed attraction element 252 in accordance with the current supplied to the coil portion. The fourth valve body 232 thus opens/closes the orifice of the fourth valve seat 234.
In this valve main body 200, there is disposed a first fluid inlet port, not shown, which communicates with the first valve body bore 203 and is arranged perpendicular to the cross section in FIG. 6. There is also disposed a second fluid inlet port, not shown, which is arranged perpendicular to the cross section in FIG. 6 as well. Furthermore, the orifice in the periphery of the first valve seat 204 and the orifice in the periphery of the second valve seat 214 are communicated with each other by means of a first inter-valve communication passage 260. There is formed a fluid outlet port 261 in a direction perpendicular to the first inter-valve communication passage 260. There is also disposed a second inter-valve communication passage 263 which is arranged in parallel to the first inter-valve communication passage 260 and communicates the orifice in the periphery of the third valve seat 224 and the orifice in the periphery of the fourth valve seat 234. A pin 227 is disposed within the second inter-valve communication passage 263 in which the respective ends of the pin 227 are connected with the third valve body 222 and the fourth valve body 232, respectively. Further, the first inter-valve communication passage 260 and the second inter-valve communication passage 263 communicate with each other by means of a return passage 262. In addition, interior of the first operation cavity 206 and interior of the fourth valve body bore 233 are communicated with each other by means of a first pilot passage 264. Also interior of the second operation cavity 216 and interior of the third valve body bore 223 are communicated with each other by means of a second pilot passage 265.
In a three-way valve 100A thus configured, when the moveable attraction element 251 is attracted to the fixed attraction element 252 according to the current supplied to the coil in the solenoid coil 250, the orifice of the fourth valve seat 234 opens and the first operation cavity 206, the first pilot passage 264, the return passage 262 and the first inter-valve communication passage 260 are all communicated through. Therefore, if the pressure in the first operation cavity 206 drops, then the first valve body 202 lifts from the first valve seat 204, thereby opening the valve. Under this circumstance, a refrigerant introduced from the aforementioned first fluid inlet port is discharged to the fluid outlet port 261. On the other hand, when the fourth valve body 232 rests on the fourth valve seat 234 for closing valve, the first valve body 202 remains closed, thereby preventing the refrigerant from being discharged to the fluid outlet port 261. When the current to the coil of the solenoid valve 250 is shut off, the moveable attraction element 251 departs from the fixed attraction element 252 downwards in the figure and the pin 227 pushed by the moveable attraction element 251 urges the third valve body 222 so as to lift from the third valve seat 224, thereby opening the valve. In this case, a refrigerant introduced from the second fluid inlet port is discharged to the fluid outlet port 261. On the other hand, when the third valve body 222 rests on the third valve seat 224 for closing valve, the second valve body 212 remains closed, thereby preventing the refrigerant from being discharged to the fluid outlet port 261.
In this three-way valve 100A, the current supplied to the solenoid valve 250 interchangeably opens or closes the orifices of the third valve portion 221 and the fourth valve portion 231, thereby controlling the pressures within the first operation cavity 206 and the second operation cavity 216 and thus the pressures of the operating fluid introduced from the first fluid inlet port and the second fluid inlet port controlling opening/closing of the first valve body 202 and the second valve body 212. Therefore, a problem arises that an actual valve opening/closing speed is delayed from a target speed of the three-way valve 100A. Also as it requires the third valve portion 221 and the fourth valve portion 231 in addition to the first valve portion 201 and the second valve portion 211, the number of parts required increases and the parts cost of the three-way valve 100A also increases. Since the first valve portion 201 and the second valve portion 211 are actuated by the operating fluid which is controlled by the third valve portion 221 and the fourth valve portion 231 according to the solenoid valve 250, narrow passageways such as the first pilot passage 264, the second pilot passage 265, the return passage 262 and the like need to be fabricated in which manufacture of the narrow passageways causes difficulties in machining. This imposes a problem of increasing manufacture cost of the three-way valve.
Patent reference 1: Japanese Patent Laid-Open Publication No. 2004-92779 (FIG. 4 and FIG. 5)